The present invention relates generally to an intake vacuum sensor for measuring intake vacuum in an intake manifold of an internal combustion engine. More specifically, the invention relates to an intake vacuum sensor having a correction device for correcting the sensor signal to compensate for varying output characteristics of the sensor.
In a conventional engine control system, engine load is determined by measuring intake vacuum in the intake manifold using an intake vacuum sensor. Generally, semi-conductor vacuum sensors and the like are used. In such a semi-conductor vacuum sensor, the output characteristic is apt to vary in accordance with increasing temperature and/or duration of use. That is, at relatively high temperatures or after a relatively long period of use, the output characteristics change according to a predetermined ratio.
Therefore, when the intake air temperature increases or the engine is driven for a long period, the determined engine load condition based on the measured intake vacuum pressure is lower than the actual engine load. Therefore, the engine control system cannot accurately effect control operation exactly corresponding to the engine load condition.